codesmell.org

http://www.mysqlperformanceblog.com/2009/08/27/looking-at-redis/
Interesting read, even though possibly biased

i almost missed Redis, but it sounds interesting:
It also has atomic operations. This is honestly the only reason I find this project interesting, because the atomic operation support that it has means that it can be turned into a best-of-breed tally server. If you are building a server to keep real-time counts of various things, [...]

keeping my eye open for data storage alternatives, i ran into this nice, thorough discussion of cassandra.